Pattern formation method

ABSTRACT

A resist film is formed by applying, on a semiconductor substrate, a resist material including a base polymer having a sulfonyl group on a side chain. The resist film is irradiated with exposing light of a wavelength of a 1 nm through 180 nm band through a mask for pattern exposure, and is developed with a developer after the pattern exposure, thereby forming a resist pattern.

BACKGROUND OF THE INVENTION

The present invention relates to a pattern formation method, and more particularly, it relates to a method of forming a resist pattern, used for forming a semiconductor device or a semiconductor integrated circuit on a semiconductor substrate, by using exposing light of a wavelength of a 1 nm through 180 nm band.

Currently, in fabrication of a large capacity semiconductor integrated circuit, typically such as a 64 Mbit dynamic random access memory (DRAM), a logic device or a system LSI with a 0.25 μm through 0.18 μm rule, a resist pattern is formed by using a resist material including a polyhydroxystyrene derivative as a main component and exposing light of KrF excimer laser (with a wavelength of a 248 nm band).

Moreover, in a pattern formation method under development for a 256 Mbit DRAM, a 1 Gbit DRAM or a system LSI with a 0.15 μm through 0.13 g m rule, ArF excimer laser operated at a shorter wavelength (of a 193 nm band) than the KrF excimer laser is to be used as the exposing light.

A resist material including a polyhydroxystyrene derivative as a main component includes an aromatic ring having a high absorbing property against light of a wavelength of a 193 nm band. Therefore, the exposing light of a wavelength of a 193 nm band cannot uniformly reach the bottom of a resist film made from this resist material, and hence, a good pattern shape cannot be obtained with this exposing light. Accordingly, the resist material including a polyhydroxystyrene derivative as a main component cannot be used when the ArF excimer laser is used as the exposing light.

Therefore, when the ArF excimer laser is used as the exposing light, a material including, as a main component, a polyacrylic acid derivative free from an aromatic ring is used as a resist material.

On the other hand, X-rays and electron beams (EB) are now examined to be used as exposing light in a pattern formation method applicable to higher resolution.

When X-rays are used as the exposing light, however, there arise various problems in an aligner and formation of a mask. Also, when EB is used as the exposing light, there arises a problem of through put, and hence, EB is not suitable to mass production. Thus, X-rays and EB are not preferred as the exposing light.

Accordingly, in order to form a resist pattern finer than 0.13 μm, it is necessary to use, as the exposing light, a laser beam with a wavelength shorter than that of the ArF excimer laser, such as a Xe₂ laser beam (with a wavelength of a 172 nm band), a F₂ laser beam (with a wavelength of a 157 nm band), a Kr₂ laser beam (with a wavelength of a 146 nm band), an ArKr laser beam (with a wavelength of a 134 nm band), an Ar₂laser beam (with a wavelength of a 126 nm band) or a soft X-ray beam (with a wavelength of a 13, 11 or 5 nm band).

Therefore, the present inventors have formed a resist pattern from a resist film of a known resist material through pattern exposure using a F₂ laser beam (with a wavelength of a 157 nm band).

However, the resultant resist pattern does not have a rectangular sectional shape but has a defective pattern shape.

SUMMARY OF THE INVENTION

In consideration of the aforementioned conventional problems, an object of the invention is forming a resist pattern in a good pattern shape by using light of a wavelength of a 1 nm through 180 nm band as exposing light.

The present inventors have earnestly examined the cause of the defective pattern shape of a resist pattern formed by using a conventionally known resist material, specifically, a resist material including a polyhydroxystyrene derivative or a polyacrylic acid derivative as a main component. As a result, it has been found that a carbonyl group included in the polyhydroxystyrene derivative or the polyacrylic acid derivative has a high absorbing property against light of a wavelength of a 1 nm through 180 nm band, so that the exposing light of a wavelength of a 1 nm through 180 nm band cannot sufficiently reach the bottom of the resist film. This seems the cause of the defective pattern shape of the resultant resist pattern.

Chemical Formula A below represents an example of the polyhydroxystyrene derivative used as a positive resist material in using KrF excimer laser, and Chemical Formula B below presents an example of the polyacrylic acid derivative used as a positive resist material in using ArF excimer laser.

The present inventors have variously studied about means for decreasing the absorbing property of a resist film against light of a wavelength of a 1 nm through 180 nm band. As a result, it has been found that the absorbing property of a resist film against light of a wavelength of a 1 nm through 180 nm band can be decreased when the resist material includes a sulfonic ester.

This is because a sulfonyl group corresponding to a light absorbing portion of a sulfonic ester has a lower absorbing property against light of a wavelength of a 1 nm through 180 nm band than a carbonyl group included in the polyhydroxystyrene derivative or the polyacrylic acid derivative.

The present invention was devised on the basis of the findings, and specifically, the first pattern formation method of this invention comprises the steps of forming a resist film by applying, on a substrate, a resist material including a base polymer having a sulfonyl group on a side chain; conducting pattern exposure by irradiating the resist film with exposing light of a wavelength of a 1 nm through 180 nm band; and forming a resist pattern by developing the resist film with a developer after the pattern exposure.

In the first pattern formation method, since the base polymer of the resist material has a sulfonyl group on the side chain, the absorbing property of the resist film against the exposing light of a wavelength of a 1 nm through 180 nm band is decreased. Therefore, the transmittance of the exposing light with a wavelength of a 1 nm through 180 nm band in the resist film is increased, and hence, the exposing light can sufficiently reach the bottom of the resist film. As a result, a resist pattern can be formed in a good pattern shape.

In the first pattern formation method, the base polymer preferably has a sulfonic ester on a side chain.

In this manner, the side chain of the base polymer is cut by the pattern exposure, so that the solubility of the base polymer in the developer can be easily changed.

In the first pattern formation method, the base polymer preferably has sulfonic acid on a side chain.

In this manner, the adhesion of the resist film onto the substrate can be improved as well as the solubility of the resist film in the developer can be controlled.

In the first pattern formation method, the resist material preferably further includes a polymer having sulfonic acid on a side chain.

In this manner, the adhesion of the resist film onto the substrate can be improved as well as the solubility of the resist film in the developer can be controlled.

In the first pattern formation method, the base polymer preferably includes a compound represented by any of the following General Formulas 1 through 5:

wherein R indicates a sulfonic ester; R₁ indicates a hydrogen atom, a hydroxyl group or an alkyl group; R₂ and R₃ are the same or different and selected from the group consisting of a hydrogen atom and an alkyl group.

In this manner, the base polymer includes an aromatic ring or a cyclic aliphatic group, and hence, the resistance against dry etching can be improved.

In the first pattern formation method, the sulfonic ester is preferably represented by any of the following Chemical Formulas 6 through 11:

wherein R₄ and R₅ are the same or different groups selected from the group consisting of an alkyl group and an aryl group;

In this manner, the absorbing property of the resist film against the exposing light of a wavelength of a 1 nm through 180 nm band can be definitely decreased.

The first pattern formation method preferably further comprises, between the step of conducting pattern exposure and the step of forming a resist pattern, a step of conducting a heat treatment on the resist film.

In this manner, decomposition of the base polymer in an exposed portion of the resist film is accelerated due to a catalytic reaction of sulfonic acid generated from the base polymer through decomposition by the exposing light.

In this case, solubility of the base polymer in the developer preferably changes in the presence of an acid, and the resist material preferably further includes an acid generator for generating an acid through irradiation with the exposing light.

In this manner, sulfonic acid generated from the base polymer through decomposition by the exposing light and the acid generated from the acid generator are heated, so as to accelerate the catalytic reaction of the acids. As a result, the decomposition of the base polymer is further accelerated in the exposed portion of the resist film.

The second pattern formation method of this invention comprises the steps of forming a resist film by applying, on a substrate, a resist material including an alkali-soluble base polymer and an agent for inhibiting dissolution of the base polymer which is made from a compound including a sulfonic ester and decomposes through irradiation with exposing light; conducting pattern exposure by irradiating the resist film with the exposing light of a wavelength of a 1 nm through 180 nm band; and forming a resist pattern by developing the resist film with a developer after the pattern exposure.

In the second pattern formation method, since the resist material includes the agent for inhibiting dissolution of the base polymer made from the compound including a sulfonic ester, the absorbing property of the resist film against the exposing light of a wavelength of a 1 nm through 180 nm band is decreased. Therefore, the transmittance of the exposing light of a wavelength of a 1 nm through 180 nm band in the resist film is increased, and hence, the exposing light can sufficiently reach the bottom of the resist film. As a result, a resist pattern can be formed in a good pattern shape.

In the second pattern formation method, the base polymer is preferably an acrylic type resin, a styrene type resin, a novolak resin or a polyolefin type resin.

In this manner, the resist film can be definitely changed to alkali-refractory by the function of the agent for inhibiting dissolution of the base polymer.

In the second pattern formation method, the agent for inhibiting dissolution of the base polymer preferably has a sulfonic ester represented by any of the following Chemical Formulas 6 through 11:

wherein R₄ and R₅ are the same or different groups selected from the group consisting of an alkyl group and an aryl group;

In this manner, the absorbing property of the resist film against light of a wavelength of a 1 nm through 180 nm band can be definitely decreased.

The second pattern formation method preferably further comprises, between the step of conducting pattern exposure and the step of forming a resist pattern, a step of conducting a heat treatment on the resist film.

In this case, the agent for inhibiting dissolution of the base polymer is preferably a compound that decomposes in the presence of an acid, and the resist material preferably further includes an acid generator for generating an acid through irradiation with the exposing light.

In the first or second pattern formation method, the exposing light is preferably a F₂ laser beam or an Ar₂ laser beam.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(a) through 1(c) are sectional views for showing procedures in a pattern formation method of any of Embodiments 1, 2 and 4 of the invention;

FIG. 2 is a diagram for showing the result of an experiment conducted for evaluating Embodiment 1 of the invention;

FIG. 3 is a diagram for showing the result of an experiment conducted for evaluating Embodiment 2 of the invention; and

FIGS. 4(a) through 4(d) are sectional views for showing procedures in a pattern formation method of any of Embodiments 3, 5 and 6.

DETAILED DESCRIPTION OF THE INVENTION Embodiment 1

A pattern formation method of Embodiment 1 will now be described with reference to FIGS. 1(a) through 1(c).

In the pattern formation method of Embodiment 1, a polymer having a sulfonyl compound, that is, a compound having a sulfonyl group, on a side chain is used as abase polymer of a resist material. The specific composition of the resist material is as follows:

Base polymer: poly((vinylsulfonylfluoride)-  2 g co-(p-tert-butoxystyrene)) (represented by Chemical Formula 12) Solvent: diglyme 20 g

First, as is shown in FIG. 1(a), the resist material having the aforementioned composition is applied by spin coating on a semiconductor substrate 10, thereby forming a resist film 11 with a thickness of 0.3 μm. At this point, since the base polymer is alkali-refractory, the resist film 11 is alkali-refractory.

Next, as is shown in FIG. 1(b), the resist film 11 is irradiated with a F₂ excimer laser beam 13 (with a wavelength of a 157 nm band) through a mask 12 for pattern exposure. In this manner, the base polymer is decomposed due to the exposing light so as to generate sulfonic acid in an exposed portion 11 a of the resist film 11, and hence, the exposed portion 11 a of the resist film 11 becomes alkali-soluble while an unexposed portion 11 b of the resist film 11 remains alkali-refractory.

Then, the resist film 11 is developed with an alkaline developer, such as a tetramethylammonium hydroxide aqueous solution. Since the exposed portion 11 a of the resist film 11 is dissolved in the developer, the unexposed portion 11 b of the resist film 11 is formed into a resist pattern 14 as is shown in FIG. 1(c). Thus, a positive resist pattern is formed in Embodiment 1.

In Embodiment 1, since the base polymer of the resist material includes a sulfonyl group on the side chain, the absorbing property of the resist film 11 against light of a wavelength of a 1 nm through 180 nm band is decreased. Therefore, the transmittance of the exposing light of a wavelength of a 1 nm through 180 nm band in the resist film 11 is increased, and hence, the exposing light can sufficiently reach the bottom of the resist film 11. As a result, the resist pattern 14 can be formed in a good pattern shape with a fine line width of 0.08 μm.

FIG. 2 is a diagram for showing the result of an experiment conducted for evaluating Embodiment 1, in which the relationship between the wavelength and the transmittance of light obtained by irradiating a polymer film with a thickness of 0.1 μm with light of a wavelength of 300 nm or less is shown. In FIG. 2, the relationship obtained from a polymer film of poly((vinylsulfonylfluoride)-co-(p-tert-butoxystyrene)) is shown as Embodiment 1; that obtained from a polymer film of the polyhydroxystyrene derivative used for KrF excimer laser is shown as Comparative Example 1; and that obtained from a polymer film of the polyacrylic acid derivative used for ArF excimer laser is shown as Comparative Example 2. As is understood from FIG. 2, the polymer film of Embodiment 1 has much higher transmittance against the F₂ laser beam with a wavelength of a 157 nm band than those of Comparative Examples 1 and 2.

Embodiment 2

A pattern formation method of Embodiment 2 will now be described with reference to FIGS. 1(a) through 1(c).

In the pattern formation method of Embodiment 2, a compound represented by the above-described General Formula 1, namely, a compound having a sulfonic ester of Chemical Formula 7 above on a side chain, is used as a base polymer of a resist material. The specific composition of the resist material is as follows:

Base polymer: a polymer  2 g represented by Chemical Formula 13 Solvent: diglyme 20 g

In Chemical Formula 13, A corresponds to sulfonic acid and B corresponds to a sulfonic ester.

First, as is shown in FIG. 1(a), the resist material having the aforementioned composition is applied by spin coating on a semiconductor substrate 10, thereby forming a resist film 11 with a thickness of 0.3 μm. At this point, since the base polymer is alkali-refractory, the resist film 11 is alkali-refractory.

Next, as is shown in FIG. 1(b), the resist film 11 is irradiated with a F₂ excimer laser beam 13 (with a wavelength of a 157 nm band) through a mask 12 for pattern exposure. In this manner, the base polymer is decomposed due to the exposing light so as to generate sulfonic acid in an exposed portion 11 a of the resist film 11, and hence, the exposed portion 11 a of the resist film 11 becomes alkali-soluble while an unexposed portion 11 b of the resist film 11 remains alkali-refractory.

Then, the resist film 11 is developed with an alkaline developer, such as a tetramethylammonium hydroxide aqueous solution. Since the exposed portion 11 a of the resist film 11 is dissolved in the developer, the unexposed portion 11 b of the resist film 11 is formed into a resist pattern 14 as is shown in FIG. 1(c). Thus, a positive resist pattern is formed in Embodiment 2.

In Embodiment 2, since the base polymer of the resist material includes a sulfonic ester on the side chain, the absorbing property of the resist film 11 against light of a wavelength of a 1 nm through 180 nm band is decreased. Therefore, the transmittance of the exposing light of a wavelength of a 1 nm through 180 nm band in the resist film 11 is increased, and hence, the exposing light can sufficiently reach the bottom of the resist film 11. As a result, the resist pattern 14 can be formed in a good pattern shape with a fine line width of 0.08 μm.

Furthermore, the base polymer of Embodiment 2 includes an aromatic ring, and hence, the resistance against dry etching can be improved.

Moreover, the base polymer of Embodiment 2 has sulfonic acid on the side chain, and hence, the adhesion of the resist film 11 onto the semiconductor substrate 10 can be improved as well as the solubility of the resist film 11 in the developer can be controlled.

Although the development is conducted after the pattern exposure of the resist film 11 without conducting a heat treatment in Embodiment 2, the resist film 11 can be heated with a hot plate or the like before the development and after the pattern exposure. In this case, since sulfonic acid generated from the base polymer through decomposition by the exposing light is heated, a catalytic reaction of the acid is caused, so as to accelerate the decomposition of the base polymer in the exposed portion 11 a of the resist film 11. Accordingly, the sensitivity of the resist film 11 is improved.

FIG. 3 is a diagram for showing the result of an experiment conducted for evaluating Embodiment 2, in which the relationship between the wavelength and the transmittance of light obtained by irradiating a polymer film with a thickness of 0.1 μm with light of a wavelength of 300 nm or less is shown. In FIG. 3, the relationship obtained from a polymer film of the compound of Chemical Formula 13 is shown as Embodiment 2; that obtained from a polymer film of the polyhydroxystyrene derivative used for KrF excimer laser is shown as Comparative Example 1; and that obtained from a polymer film of the polyacrylic acid derivative used for ArF excimer laser is shown as Comparative Example 2. As is understood from FIG. 3, the polymer film of Embodiment 2 has much higher transmittance against the F₂ laser beam with a wavelength of a 157 nm band than those of Comparative Examples 1 and 2.

Embodiment 3

A pattern formation method of Embodiment 3 will now be described with reference to FIGS. 4(a) through 4(d).

In the pattern formation method of Embodiment 3, a compound represented by the above-described General Formula 3, namely, a compound having a sulfonic ester of Chemical Formula 6 above on a side chain, is used as a base polymer of a resist material. The specific composition of the resist material is as follows:

Base polymer: a polymer   2 g represented by Chemical Formula 14 Acid generator: triphenylsulfonium triflate 0.04 g Solvent: diglyme   20 g

In Chemical Formula 14, A corresponds to sulfonic acid and B corresponds to a sulfonic ester.

First, as is shown in FIG. 4(a), the resist material having the aforementioned composition is applied by spin coating on a semiconductor substrate 20, thereby forming a resist film 21 with a thickness of 0.3 μm. At this point, the base polymer is alkali-refractory, and hence, the resist film 21 is alkali-refractory.

Next, as is shown in FIG. 4(b), the resist film 21 is irradiated with a F₂ excimer laser beam 23 (with a wavelength of a 157 nm band) through a mask 22 for pattern exposure. Thus, the base polymer is decomposed by the exposing light in an exposed portion 21 a of the resist film 21 so as to generate sulfonic acid, and hence, the exposed portion 21 a of the resist film 21 becomes alkali-soluble while an unexposed portion 21 b of the resist film 21 remains alkali-refractory. Also, an acid is generated from the acid generator in the exposed portion 21 a of the resist film 21 while no acid is generated in the unexposed portion 21 b of the resist film 21.

Then, as is shown in FIG. 4(c), the semiconductor substrate 20 together with the resist film 21 are heated on a hot plate 24. Thus, sulfonic acid generated from the base polymer through decomposition by the exposing light and the acid generated from the acid generator are heated so as to cause a catalytic reaction of the acids. This catalytic reaction accelerates the decomposition of the base polymer in the exposed portion 21 a of the resist film 21. Accordingly, the sensitivity of the resist film 21 is further improved.

Thereafter, the resist film 21 is developed with an alkaline developer, such as a tetramethylammonium hydroxide aqueous solution. Since the exposed portion 21 a of the resist film 21 is dissolved in the developer, the unexposed portion 21 b of the resist film 21 is formed into a resist pattern 25 as is shown in FIG. 4(d). Thus, a positive resist pattern is formed in Embodiment 3.

In Embodiment 3, since the resist material includes the base polymer having a sulfonic ester on the side chain, the absorbing property of the resist film 21 against light of a wavelength of a 1 nm through 180 nm band is decreased. Therefore, the transmittance of the exposing light of a wavelength of a 1 ran through 180 nm band in the resist film 21 is increased, and hence, the exposing light can sufficiently reach the bottom of the resist film 21. As a result, the resist pattern 25 can be formed in a good pattern shape with a fine line width of 0.08 μm.

Furthermore, since the base polymer of Embodiment 3 includes a cyclic aliphatic group, the resistance against dry etching can be improved.

Moreover, since the base polymer of Embodiment 3 has sulfonic acid on the side chain, the adhesion of the resist film 21 onto the semiconductor substrate 20 can be improved as well as the solubility of the resist film 21 in the developer can be controlled.

Embodiment 4

A pattern formation method of Embodiment 4 will now be described with reference to FIGS. 1(a) through 1(c).

In the pattern formation method of Embodiment 4, a resist material includes an alkali-soluble base polymer and an agent for inhibiting dissolution of the base polymer (hereinafter referred to as the dissolution inhibiting agent) of a compound including a sulfonic ester represented by Chemical Formula 8 above (wherein R₄ and R₅ are the same or different groups selected from the group consisting of an alkyl group and an aryl group). The specific composition of the resist material is as follows:

Base polymer: novolak resin   2 g Dissolution inhibiting agent: a compound 0.4 g represented by Chemical Formula 15 Solvent: diglyme  20 g

First, as is shown in FIG. 1(a), the resist material having the aforementioned composition is applied by spin coating on a semiconductor substrate 10, thereby forming a resist film 11 with a thickness of 0.3 μm. At this point, although the base polymer is alkali-soluble, the resist film 11 is alkali-refractory due to the function of the dissolution inhibiting agent.

Next, as is shown in FIG. 1(b), the resist film 11 is irradiated with a F₂ excimer laser beam 13 (with a wavelength of a 157 nm band) through a mask 12 for pattern exposure. In this manner, the dissolution inhibiting agent is decomposed due to the exposing light so as to generate sulfonic acid in an exposed portion 11 a of the resist film 11, and hence, the exposed portion 11 a of the resist film 11 becomes alkali-soluble while an unexposed portion 11 b of the resist film 11 remains alkali-refractory.

Then, the resist film 11 is developed with an alkaline developer, such as a tetramethylammonium hydroxide aqueous solution. Since the exposed portion 11 a of the resist film 11 is dissolved in the developer, the unexposed portion 11 b of the resist film 11 is formed into a resist pattern 14 as is shown in FIG. 1(c). Thus, a positive resist pattern is formed in Embodiment 4.

In Embodiment 4, since the resist material includes the dissolution inhibiting agent of the compound having a sulfonic ester, the absorbing property of the resist film 11 against light of a wavelength of a 1 nm through 180 nm band is decreased. Therefore, the transmittance of the exposing light of a wavelength of a 1 nm through 180 nm band in the resist film 11 is increased, and hence, the exposing light can sufficiently reach the bottom of the resist film 11. As a result, the resist pattern 14 can be formed in a good pattern shape with a fine line width of 0.08 μm.

Furthermore, the dissolution inhibiting agent of Embodiment 4 includes an aromatic ring, and hence, the resistance against dry etching can be improved.

Although the development is conducted after the pattern exposure of the resist film 11 without conducting a heat treatment in Embodiment 4, the resist film 11 can be heated with a hot plate or the like before the development and after the pattern exposure. In this case, since sulfonic acid generated from the dissolution inhibiting agent through decomposition by the exposing light is heated, a catalytic reaction of the acid is caused, so as to accelerate the decomposition of the dissolution inhibiting agent in the exposed portion 11 a of the resist film 11. Accordingly, the sensitivity of the resist film 11 is improved.

Embodiment 5

A pattern formation method of Embodiment 5 will now be described with reference to FIGS. 4(a) through 4(d).

In the pattern formation method of Embodiment 5, a resist material includes an alkali-soluble base polymer and a dissolution inhibiting agent including a compound having a sulfonic ester represented by Chemical Formula 9 above. The specific composition of the resist material is as follows:

Base polymer: polyhydroxystyrene   2 g Dissolution inhibiting agent: a compound  0.4 g represented by Chemical Formula 16 Acid generator: triphenylsulfonium triflate 0.04 g Solvent: diglyme   20 g

First, as is shown in FIG. 4(a), the resist material having the aforementioned composition is applied by spin coating on a semiconductor substrate 20, thereby forming a resist film 21 with a thickness of 0.3 μm. At this point, although the base polymer is alkali-soluble, the resist film 21 is alkali-refractory due to the function of the dissolution inhibiting agent.

Next, as is shown in FIG. 4(b), the resist film 21 is irradiated with a F₂ excimer laser beam 23 (with a wavelength of a 157 nm band) through a mask 22 for pattern exposure. Thus, the dissolution inhibiting agent is decomposed by the exposing light in an exposed portion 21 a of the resist film 21 so as to generate sulfonic acid, and hence, the exposed portion 21 a of the resist film 21 becomes alkali-soluble while an unexposed portion 21 b of the resist film 21 remains alkali-refractory. Also, an acid is generated from the acid generator in the exposed portion 21 a of the resist film 21 while no acid is generated in the unexposed portion 21 b of the resist film 21.

Then, as is shown in FIG. 4(c), the semiconductor substrate 20 together with the resist film 21 are heated on a hot plate 24. Thus, sulfonic acid generated from the dissolution inhibitingagent through decomposition by the exposing light and the acid generated from the acid generator are heated so as to cause a catalytic reaction of the acids. This catalytic reaction accelerates the decomposition of the dissolution inhibiting agent in the exposed portion 21 a of the resist film 21. Accordingly, the sensitivity of the resist film 21 is further improved.

Thereafter, the resist film 21 is developed with an alkaline developer, such as a tetramethylammonium hydroxide aqueous solution. Since the exposed portion 21 a of the resist film 21 is dissolved in the developer, the unexposed portion 21 b of the resist film 21 is formed into a resist pattern 25 as is shown in FIG. 4(d). Thus, a positive resist pattern is formed in Embodiment 5.

In Embodiment 5, since the resist material includes the dissolution inhibiting agent of the compound having a sulfonic ester, the absorbing property of the resist film 21 against light of a wavelength of a 1 nm through 180 nm band is decreased. Therefore, the transmittance of the exposing light of a wavelength of a 1 nm through 180 nm band in the resist film 21 is increased, and hence, the exposing light can sufficiently reach the bottom of the resist film 21. As a result, the resist pattern 25 can be formed in a good pattern shape with a fine line width of 0.08 μm.

Furthermore, since the dissolution inhibiting agent of Embodiment 5 includes an aromatic ring, the resistance against dry etching can be improved.

EMBODIMENT 6

A pattern formation method of Embodiment 6 will now be described with reference to FIGS. 4(a) through 4(d).

In the pattern formation method of Embodiment 6, a resist material includes an alkali-soluble base polymer and a dissolution inhibiting agent of a polymer having a sulfonic ester represented by Chemical Formula 7 above on a side chain. The specific composition of the resist material is as follows:

Base polymer: polyhydroxystyrene  1.5 g Dissolution inhibiting agent: a polymer   1 g represented by Chemical Formula 17 Acid generator: triphenylsulfonium triflate 0.04 g Solvent: diglyme   20 g

In Chemical Formula 17, A corresponds to sulfonic acid and B corresponds to a sulfonic ester.

First, as is shown in FIG. 4(a), the resist material having the aforementioned composition is applied by spin coating on a semiconductor substrate 20, thereby forming a resist film 21 with a thickness of 0.3 μm. At this point, although the base polymer is alkali-soluble, the resist film 21 is alkali-refractory due to the function of the dissolution inhibiting agent.

Next, as is shown in FIG. 4(b), the resist film 21 is irradiated with a F₂ excimer laser beam 23 (with a wavelength of a 157 nm band) through a mask 22 for pattern exposure. Thus, the dissolution inhibiting agent is decomposed by the exposing light in an exposed portion 21 a of the resist film 21 so as to generate sulfonic acid, and hence, the exposed portion 21 a of the resist film 21 becomes alkali-soluble while an unexposed portion 21 b of the resist film 21 remains alkali-refractory. Also, an acid is generated from the acid generator in the exposed portion 21 a of the resist film 21 while no acid is generated in the unexposed portion 21 b of the resist film 21.

Then, as is shown in FIG. 4(c), the semiconductor substrate 20 together with the resist film 21 are heated on a hot plate 24. Thus, sulfonic acid generated from the dissolution inhibiting agent through decomposition by the exposing light and the acid generated from the acid generator are heated so as to cause a catalytic reaction of the acids. This catalytic reaction accelerates the decomposition of the dissolution inhibiting agent in the exposed portion 21 a of the resist film 21. Accordingly, the sensitivity of the resist film 21 is further improved.

Thereafter, the resist film 21 is developed with an alkaline developer, such as a tetramethylammonium hydroxide aqueous solution. Since the exposed portion 21 a of the resist film 21 is dissolved in the developer, the unexposed portion 21 b of the resist film 21 is formed into a resist pattern 25 as is shown in FIG. 4(d). Thus, a positive resist pattern is formed in Embodiment 6.

In Embodiment 6, since the resist material includes the dissolution inhibiting agent of the compound having a sulfonic ester, the absorbing property of the resist film 21 against light of a wavelength of a 1 nm through 180 nm band is decreased. Therefore, the transmittance of the exposing light of a wavelength of a 1 nm through 180 nm band in the resist film 21 is increased, and hence, the exposing light can sufficiently reach the bottom of the resist film 21. As a result, the resist pattern 25 can be formed in a good pattern shape with a fine line width of 0.08 μm.

Furthermore, since the base polymer of Embodiment 6 includes an aromatic ring, the resistance against dry etching can be improved.

In Embodiment 2 or 3, any one of the polymers represented by General Formulas 1 through 5 can be used as the base polymer, but the base polymer is not limited to them.

In Embodiment 2 or 3, a polymer having any of sulfonic esters represented by Chemical Formulas 6 through 11 on the side chain can be used as the base polymer, but the base polymer is not limited to them.

In Embodiment 2 or 3, a polymer having a sulfonic ester and sulfonic acid on the side chains is used as the base polymer, which can be replaced with a mixture of a polymer having a sulfonic ester on a side chain and a polymer having sulfonic acid on a side chain.

In any of Embodiments 3 through 5, a compound including any one of sulfonic esters represented by Chemical Formulas 6 through 11 can be used as the dissolution inhibiting agent, but the dissolution inhibiting agent is not limited to them.

In any of Embodiments 4 through 6, the alkali-soluble base polymer can be an acrylic type resin, a styrene type resin, a novolak resin or a polyolefin type resin, but the alkali-soluble base polymer is not limited to them.

In any of Embodiments 3, 5 and 6, any of onium salts such as sulfonium salt and iodonium salt, sulfonic esters, diazodisulfonylmethanes and ketosulfone compounds can be appropriately used as the acid generator.

In each of Embodiments 1 through 6, any of a Xe₂ laser beam (with a wavelength of a 172 nm band), a F₂ laser beam (with a wavelength of a 157 nm band), a Kr₂ laser beam (with a wavelength of a 146 nm band), an ArKr laser beam (with a wavelength of a 134 nm band), an Ar₂ laser beam (with a wavelength of a 126 nm band) and a soft X-ray beam (with a wavelength of a 13, 11 or 5 nm band) can be used as the exposing light.

Furthermore, although a positive resist pattern is formed by removing the exposed portion of the resist film with the alkaline developer in each of Embodiments 1 through 6, a negative resist pattern can be formed instead by removing the unexposed portion of the resist film with a developer of an organic solvent. 

What is claimed is:
 1. A pattern formation method comprising the steps of: forming a resist film by applying, on a substrate, a resist material including a base polymer having a sulfonyl group on a side chain; conducting pattern exposure by irradiating said resist film with exposing light of a wavelength of a 1 nm through 180 nm band; and forming a resist pattern by wet development for said resist film with a developer after the pattern exposure.
 2. The pattern formation method of claim 1, wherein said base polymer has a sulfonic ester on a side chain.
 3. The pattern formation method of claim 1, wherein said base polymer has sulfonic acid on a side chain.
 4. The pattern formation method of claim 1, wherein said resist material further includes a polymer having sulfonic acid on a side chain.
 5. The pattern formation method of claim 1, wherein said base polymer includes a compound represented by any of the following General Formulas 1 through 5:

wherein R indicates a sulfonic ester; R₁ indicates a hydrogen atom, a hydroxyl group or an alkyl group; R₂ and R₃ are the same or different and selected from the group consisting of a hydrogen atom and an alkyl group.
 6. The pattern formation method of claim 2, wherein said sulfonic ester is represented by any of the following Chemical Formulas 6 through 11:

 wherein R₄ and R₅ are the same or different groups selected from the group consisting of an alkyl group and an aryl group;


7. The pattern formation method of claim 1 further comprising, between the step of conducting pattern exposure and the step of forming a resist pattern, a step of conducting a heat treatment on said resist film.
 8. The pattern formation method of claim 7, wherein solubility of said base polymer in said developer changes in the presence of an acid, and said resist material further includes an acid generator for generating an acid through irradiation with said exposing light.
 9. A pattern formation method comprising the steps of: forming a resist film by applying, on a substrate, a resist material including an alkali-soluble base polymer and an agent for inhibiting dissolution of said base polymer which is made from a compound including a sulfonic ester and decomposes through irradiation with exposing light; conducting pattern exposure by irradiating said resist film with said exposing light of a wavelength of a 1 nm through 180 nm band; and forming a resist pattern by wet development for said resist film with a developer after the pattern exposure.
 10. The pattern formation method of claim 9, wherein said base polymer is an acrylic type resin, a styrene type resin, a novolak resin or a polyolefin type resin.
 11. The pattern formation method of claim 9, wherein said agent for inhibiting dissolution of said base polymer has a sulfonic ester represented by any of the following Chemical Formulas 6 through 11:

 wherein R₄ and R₅ are the same or different groups selected from the group consisting of an alkyl group and an aryl group;


12. The pattern formation method of claim 9 further comprising, between the step of conducting pattern exposure and the step of forming a resist pattern, a step of conducting a heat treatment on said resist film.
 13. The pattern formation method of claim 12, wherein said agent for inhibiting dissolution of said base polymer is a compound that decomposes in the presence of an acid, and said resist material further includes an acid generator for generating an acid through irradiation with said exposing light.
 14. The pattern formation method of claim 1, wherein said exposing light is an Xe₂ laser beam, a F₂ laser beam, a Kr₂ laser beam, an ArKr laser beam or an Ar₂ laser beam.
 15. The pattern formation method of claim 1, wherein said exposing light is a soft x-ray beam.
 16. The pattern formation method of claim 9, wherein said exposing light is an Xe₂ laser beam, a F₂ laser beam, a Kr₂ laser beam, an ArKr laser beam or an Ar₂ laser beam.
 17. The pattern formation method of claim 9, wherein said exposing light is a soft x-ray beam. 